C# Tutorial: Hello World

C# Tutorial Lesson 1: Hello World

The simplest C# program is, of course, Hello World. You will need a C# compiler, which comes as a part of .Net Framework SDK. In your favorite text editor enter the following code:

class Hello
//This program displays Hello World
{
    static public void Main()
    {
       System.Console.WriteLine("Hello World");
    }
}

Save this file as myhello.cs and type

csc myhello.cs

If you haven't made any typos, something like:

will appear in your command prompt window. The C# compiler will have created an executable code as a binary file in the PE format named myhello.exe. By simply typing myhello you will see

Hello World

What does this simple C# program look like? Java! Note that all methods end with semicolons and Main() method is a part of class Hello. Statements are enclosed in braces. Like in Java and C/C++, every program has a Main() entry point. However, in Java the name of the program should be the same as the name of the class. There is no such restriction in C#.

System.Console is a namespace that takes care of console I/O (see exercise 5). Other methods of System.Console include Write method, which does not add a carriage return at the end of the line, and ReadLine, which gets user input from the console.

As the next step in learning C#, we will write a Windows program that displays "Hello World" dialog:

using System;
using System.Windows.Forms;
class Hello
{
    static void Main()
    {
         MessageBox.Show("Hello World");
    }
}

Running this code will produce the following dialog

Hello World dialog

Finally, we will write a Web application that displays "Hello World" in the browser window:

<%@ Page language="C#" %>
<html>
<head>
<title>
Hello C#
</title>
</head>
<body>
<p><% Response.Write("Hello World");%></p>
</body>
</html>

This code needs to be saved as a file with an aspx extension (e.g. helloWeb.aspx) and placed in a virtual folder (e.g. c:\inetpub\wwwroot). To run this code, type the URL pointing to the file in the browser (e.g http://localhost/helloWeb.aspx)

Exercise

Write a routine that asks a user some questions and gives meaningful output based on her answers.

Home

C# Tutorial

XML Tutorial

C# Review

C# Books

C# Tutorial Lesson 1: Hello World